General purpose dump trucks are conventionally constructed with a load-carrying bed mounted for tilting movement. The load-carrying bed has a dump body with a rear opening closed by a tailgate pivoted thereto at the top of the dump body. The tailgate is held closed at the bottom of the dump body by grab hooks on opposite sides of the dump body. To unload the dump body, the forward end of the dump body is raised and the tailgate is released from its closed position, letting the material retained in the dump body flow by gravity through the opening in the rear of the body. The material is spread by moving the truck forward as the material is released. The thickness of the spread material is controlled by the speed of the truck and the size of the opening or gap defined by the bottom edge of the tailgate and the bottom edge of the opening in the dump body.
Two short chains are permanently attached to the underside of the dump body adjacent the opening. Welded to the tailgate, directly above each chain, is a plate which has vertical slots therein to accept any one of the chain links adjacent the free ends of the chains. Before the spreading process begins, the driver adjusts the size of the opening at the tailgate by selecting the appropriate chain link in each chain and retaining the link in the slot.
After adjusting the chains, the driver gets into the cab, raises the dump body and drives the truck forward. At the location where the driver wants to start spreading the load, he releases the grab hooks to allow the tailgate to open against the chains. If all goes well, the material will be spread smoothly and evenly. However, sticky material, chunks of mud, rocks, cold asphalt or other foreign objects can plug the opening and thus stop the flow of material. When this happens, someone must close the tailgate approximately 2 to 4 inches to release the chains from the slots so that the jamming material can be removed from the opening. In order to close the tailgate 2 to 4 inches, a shovel, large hand hammer or steel bar must be used to dislodge the jammed material from the opening. This results in considerable aggravation and lost time. The lost time can range from a few minutes to a few hours.
For the foregoing reasons, there is a need for an arrangement to facilitate releasing the chains without having to resort to using hand tools to dislodge materials from between the tailgate and dump body so that the tailgate can be moved a short distance toward the closed position in order to release tension on the chains.